This invention is an improvement of my invention in application Ser. No. 07/862,800 filed jointly On Apr. 3, 1992 for "System for Imprinting Patient-Identifying Barcodes Onto Medical X-rays", now U.S. Pat. No. 5,288,977.
The present invention relates to the barcoding of x-ray and similar film with sufficient clarity to eliminate or minimize the risk that an error in identification will result.
Present methods of placing identification on x-ray films includes the common method of using a paper or card "negative" through which light is passed creating the image of the paper containing the typewritten information on the film. This method requires that the card or paper be in direct contact with the film and the entire procedure be done in a darkroom because the film must be removed from the x-ray cassette. Another, more sophisticated method involves using the same basic paper or card method in an opaque projector which optically focuses the image on the film within the cassette through a "window" opening in the cassette. This method can be used outside the darkroom and also in the darkroom directly on the film, if necessary.
Newer devices, known as ID cameras, such as Kodak's unit, incorporate a LCD device which adds the time and date to the other information. These LCD's are similar to those used on watches, etc. They are opaque and read the way a camera reads, that is, from one side and are used within the opaque projector device just as the opaque paper or card is used.
Although it may be possible to place a barcode on the film using the paper system, the barcode would have to be first printed on the paper, then the paper would be used in the same way as the current placing of alphanumeric characters on the film. It might also be possible to place the barcode on the LCD and then project this image on the film with the opaque projector. There are some difficulties with this because where the device might be good enough for characters to be read by eye, the barcode image must be accurate and well defined for it to be readable. The cost of the optics to do this is much greater than using the simple system I have devised.
In our earlier applications there is described a system for marking x-ray film with a barcode which is formed by an LCD and projected directly onto the film.
In order for the barcode to appear on the x-ray film sufficiently sharp and clear to avoid errors in reading the code, it is necessary that the LCD be mounted very close to the film.
If a collimated light source were projected through the LCD, the image cast on the film would theoretically be sharp at any distance from the LCD although, from a practical point of view, there are limitations which prevent using large distances. Also, providing a collimated light source involves the use of complex lens systems involving significantly higher costs and greater space requirements.